1. Field of the Invention
The present invention relates to a battery using a carbon material as an anode active material.
2. Description of the Related Art
In recent years, downsizing and weight saving of portable electronic devices represented by a mobile phone, a PDA (Personal Digital Assistant), and a notebook personal computer have been actively promoted. As a part thereof, improving an energy density of a battery as a driving power source for such electronic devices, in particular, of a secondary battery has been strongly desired.
As a secondary battery capable of providing a high energy density, for example, the secondary batteries using lithium (Li) as an electrode reactant are known. Specially, the lithium ion secondary batteries using a carbon material capable of inserting and extracting lithium for the anode are widely used practically. However, in the lithium ion secondary battery using the carbon material for the anode, the technology has been already developed to the degree close to its theoretical capacity. Therefore, as a method to further improve the energy density, it has been considered that the thickness of the active material layer is increased to increase the ratio of the active material layer in the battery, and the ratios of the current collector and the separator are lowered (refer to Japanese Unexamined Patent Application Publication No. 9-204936).